1. Field of the Invention
The present invention relates to air release valves and, more particularly, to an atmospheric compensating automatic air release valve.
2. Description of the Related Art
A typical automatic air release valve is normally open when installed so that air can be vented to atmosphere through an air release orifice. As the system is filled with water and liquid enters the automatic air release valve, the float mounted therewithin is raised and activates the mechanism to shut the air release orifice. When the orifice is shut, the air release valve becomes pressurized. The orifice remains closed until such time as air bubbles enter the air release valve and displace the water therewithin. Once the water is displaced, the mechanism and float are no longer submerged. A suction force due to the pressure differential between the interior of the valve housing and atmosphere tends to hold the mechanism in sealing relation to the air release orifice. However, such valves are designed so that the combined weight of the mechanism and the float is sufficient to open the orifice against the internal pressure. The size of the air release orifice determines, for a given valve mechanism, the maximum pressure with which the valve will operate.
Thus, typical automatic air release valves have a specific high pressure limit up to which point they will open and allow entrapped air to escape. Beyond the high pressure limit, the typical automatic air release valve will not open. Therefore, once the size of the air release valve body and internal valving mechanism have been designed for a specific operating pressure or pressure range, the only way that the operating pressure can be changed is by changing the size of the air release orifice.
This functionally limiting characteristic of conventional air release valves requires that when design engineers specify air release valves for their pipeline, they select one which will satisfy the highest pressure anticipated in the pipeline and will ignore the fact that there are a variety of lesser pressures in line. In doing so, the advantages of using a variety of orifices to gain maximum venting capacity at each high point is sacrificed. Indeed, the higher the operating pressure to which the air release valve is exposed, the smaller orifice employed. If a conventional air release valve is employed in line and selected in anticipation of the maximum pressure in the entire line, then the air release valves will necessarily have a relatively small orifice and thus relatively low air venting capacity irrespective of the fact that at certain points along the line the maximum pressure would be far lower than the maximum for the entire line.
It would be desirable, therefore, to provide an air release valve having an unlimited operating pressure range without having to change the size of the valving mechanism and/or the size of the air release orifice so that advantage can be taken of maximum venting capacity.